Stone metering system for railroad track maintenance vehicle

ABSTRACT

A stone metering system for a railroad track maintenance vehicle providing improved accuracy in stone delivery. The system includes a surge hopper, a number of metering augers, and a corresponding number of splitters. The metering augers convey ballast stones from the surge hopper to the corresponding splitters, which divide the stones evenly between a number of blow tubes. The pitch of the auger screw flights is increased from the inlet end of the screw to &#34;expand&#34; the stone and reduce the production of fines. In addition, the diameter of the final screw flight is reduced at the outlet end of the auger to provide a consistent and even flow of stone into the splitters. The splitters are dynamically adjustable to provide even distribution between the blow tubes regardless of the cant to the rails. The desired amount of stone is delivered to the tubes by rotating the auger screw the number of full or partial revolutions associated with the amount. In an alternative embodiment, each of the metering augers is replaced by a conveyor having a belt divided into a series of uniformly sized compartments each conveying the same quantity of stone. The desired amount of stone is delivered to the tubes by driving the belt so that a desired number of compartments are emptied into the splitter.

BACKGROUND OF THE INVENTION

The present invention relates to a stone or ballast metering system fora railroad track maintenance vehicle.

The tremendous forces exerted on railroad track as trains and other railvehicles move over the track results in displacement of the rails andties within the stones or "ballast." In particular, the verticalposition of the ties within the track ballast changes, usually with theties settling deeper into the ballast, changing the height of the track.Accordingly, periodic realignment of the railroad track within the bedis necessary to restore the track to its desired configuration.Realignment is performed by either a tamper or a stone blower.

A tamper includes a jacking mechanism which grasps and lifts the railsand ties attached thereto. The tamper also includes blades whichpenetrate the ballast and are vibrated to force the ballast back underthe lifted ties to return the track to a desired vertical position.

A stone blower also includes a jacking mechanism which grasps and liftsthe rails and ties. However, rather than blades, the stoneblowerincludes tubes which penetrate the ballast and force new or additionalstones beneath the ties. More particularly, a stoneblower is a vehiclethat travels upon the track rails and carries a track lifting device, anumber of workheads, a source of compressed air, a supply of ballaststones, and a stone metering system. The workheads each include one ormore blow tubes through which ballast stone is blown by compressed air.In operation, the track lifting device raises the track rails and theties to which the rails are secured, which creates a void beneath theties. The blow tubes are forced into the track bed adjacent the raisedties to direct a measured quantity of ballast stone under the ties. Theamount of stone is determined by the desired amount of lift.

The amount of ballast stone blown beneath each tie is crucial to theproper level of the tracks. The ballast stone must be delivered to theworkheads in the proper quantity. It is the function of the stonemetering system to ensure that the proper quantity of stone is deliveredfrom the supply of ballast stones to the workheads.

In the past, vibratory chute style stone metering systems have beenemployed. This type of system utilizes a feeder pan to receive thedesired amount of stone by weight. The measured stone is passed in bulkto a vibratory chute type feeder. The vibratory chute feeds the measuredstone to the blow tubes at a fairly constant rate. This type of stonemetering system is difficult to incorporate into the configuration andprofile of the stoneblower. In addition, the precision of this design isadversely affected by a variety of elements, such as track cant, stonemoisture content, track grade, and cycle time.

Another known type of stone metering system includes a number of augerconveyors which convey and meter stone to the workheads. Each augerconveyor includes an auger screw housed within a casing. As the augerscrew is rotated, stone is conveyed along the flights of the screw. Theamount of stone supplied to the blow tubes is measured by calculatingthe flow rate of the auger conveyor and monitoring the revolutions ofthe auger screw. Auger systems include an auger conveyor for each blowtube. Auger type stone metering systems have a variety of shortcomings.First, degradation (i.e. pulverization) of the stone during theconveying process produces "fines" (i.e. powdered stone) which reducesthe accuracy of the metering system. Second, pulsed output of stone fromthe metering auger can lead to uneven distribution of stone. Third, therequired multiplicity of augers is relatively expensive, bulky, anddifficult to incorporate into the profile of a stoneblower.

SUMMARY OF THE INVENTION

The aforementioned problems are overcome by the present inventionwherein an auger-type stone metering system includes augers that eachfeed multiple blow tubes. More particularly, the stone metering systemincludes a number of metering augers and a splitter for each auger. Themetering augers convey the ballast stones upward along the flights of arotating auger screw housed within a cylindrical casing. At the upperend, the stone is expelled onto the corresponding splitter. Eachsplitter includes two adjacent feed compartments which divide the stonesupplied by the metering auger between two adjacent blow tubes. Thesplitters are moveable to provide the desired distribution between theblow tubes even when the stoneblower is tilted due to significant cantto the rails.

In a second aspect of the invention, the screw within the auger has aunique configuration to expel stone at a more uniform rate thanpreviously has been possible. The pitch of the auger screw flights isincreased between the inlet end and the outlet end to "expand" the stonereducing the production of fines through grinding and shearing. Inaddition, the diameter of the auger screw is tapered down or reducedtoward the outlet end of the auger to improve consistent and even flowof stone onto the splitters.

A second embodiment of the invention incorporates a different meteringconveyor. Specifically, each metering conveyor is a belt having a seriesof uniform, adjacent compartments along its length-somewhat like anice-cube tray. Each compartment holds a known quantity of stone.Therefore, the stone can be metered by operating the conveyor to dump adesired number of compartment of stone onto the associated splitter.Preferably, a distribution plate is positioned over each conveyor toensure that each compartment is evenly filled.

The present invention provides an accurate and reliable stone meteringsystem for use in track maintenance vehicles. The variable-pitch andvariable-diameter auger screw reduces pulverization of stone during theconveying process and makes the flow of stone out of the auger moreconsistent. In addition, the adjustable splitters compensate for a widevariety of flow factors, such as track cant, material characteristics,stone moisture content, track grade, and cycle time. Further, thesplitters enable the number of metering augers to be cut in half therebyreducing the cost and profile of the system.

These and other objects, advantages, and features of the invention willbe more fully understood and appreciated by reference to the detaileddescription of the preferred embodiment and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is a fragmentary side elevational view of a portion of astoneblower showing the surge hopper, the work head, and the stoneconveying/metering system of the present invention;

FIG. 1b is a fragmentary side elevational view of a second portion ofthe stoneblower to the right of FIG. 1a showing a portion of theconveyor system for moving stone from the main hopper to the surgehopper;

FIG. 1c is a fragmentary side elevational view of a third portion of thestoneblower to the right of FIG. 1c showing the main hopper and aportion of the conveyor system for moving stone from the main hopper tothe surge hopper;

FIG. 2 is a side elevational view of the surge hopper and one stoneauger;

FIG. 3 is a perspective view of the surge hopper;

FIG. 4 is a top plan view of the surge hopper and stone augers;

FIG. 5 is a sectional view of a stone metering auger showing the screw;

FIG. 6 is a perspective view of a metering conveyor according to analternative embodiment; and

FIG. 7 is a side elevational view of the surge hopper and alternativemetering conveyor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The stone metering system of the present invention is illustrated in thedrawings and generally designated 10. By way of example, and not by wayof limitation, the stone metering system will be described in connectionwith a stoneblower 12. The stoneblower 12 (FIGS. 1a-c) includes asuperstructure 14 carrying a supply of ballast stones 18, a plurality ofworkheads 22a-d, a stone replenishing system 70, and a stone meteringsystem 10. Each workhead 22a-d includes a pair of blowing tubes 30a-b.The stoneblower 12 also includes wheels 13 for supporting thesuperstructure 14 upon the rails and an engine 15 for moving thestoneblower 12 along the track.

The stoneblower 12 travels along track to be realigned. A conventionaltrack lifting device (not shown) carried on the superstructure 14 raisesboth the track rails and the ties to which the rails are secured,thereby creating a void beneath the raised ties. The workhead 22a-dforces the pair of blowing tubes 30a-b into the track bed adjacent toand straddling the raised track ties. Stone is then blown through theblowing tubes 30a-b into the voids beneath the raised ties. The stone ispropelled through the blowing tubes 30a-b by compressed air that issupplied by any conventional means, such as an air compressor. Uponcompletion, the workhead 22a-d withdraws the blowing tubes 30a-b; andthe stoneblower 12 indexes to the next tie.

I. Stone Replenishing System

A stone replenishing system 70 is provided to move stone from the mainhopper 18 to the stone metering system 10 when the level of stone in thesurge hopper 24 becomes low. While the surge hopper 24 will be describedin greater detail below in conjunction with the stone metering system10, a basic knowledge of its general structure and function arenecessary for a clear understanding of the stone replenishing system 70.In general, the surge hopper 24 is an intermediate storage compartmentthat receives stone from the main hopper 72 and feeds that stone to thestone metering system 10. The surge hopper 24 has a wide but rathershallow construction which allows it to fit within the profile of themaintenance vehicle (See FIGS. 2-4). As a result of the relativelyshallow nature of the surge hopper 24, the supply of stone carriedtherein must be periodically replenished by the stone replenishingsystem 70.

Referring again to FIGS. 1a-c, the stone replenishing system 70generally includes a main hopper 72, a main auger 74, a cleat conveyor76, a stone scalper 78, a horizontal conveyor 80, a diverter assembly150, and a plurality of stone level sensors 84a-f (See FIGS. 3 and 4).The main hopper 72 is supported upon the superstructure and carries thesupply of ballast stones 18. The stone replenishing system 70 iscontrolled by the control system of the maintenance vehicle whichmonitors the stone level sensors 84a-d to periodically activate thesystem 70.

The stone level sensors 84a-f are mounted within the surge hopper 24 tomonitor the level of stone therein (See FIGS. 3 and 4). Because of thewide and shallow construction of the surge hopper 24, stone level mayvary at opposite sides of surge hopper 24. Accordingly, the stone levelsensors 84a-f are aligned in two rows located on opposite sides of thesurge hopper 24. Each row of sensors includes a high 84a and 84d, low84b and 84e, and empty 84c sensor. In a preferred embodiment, the stonelevel sensors 84a-f are photoelectric sensors. However, a variety ofother types of sensors may be employed and the incorporation thereofwill be apparent to those of ordinary skill in the art.

Just as it is important to independently monitor the level of stone atopposite sides of the hopper 24, it is also important to independentlyfeed stone to opposite sides of the hopper 24. As perhaps bestillustrated in FIGS. 3 and 4, the diverter assembly 150 is mountedadjacent the end of the horizontal conveyor 80 to control theproportional flow of stone to opposite sides of the surge hopper 24. Ina preferred embodiment, the diverter assembly 150 is mounted above thesurge hopper 24 in alignment with the horizontal conveyor 80 andincludes three diverter plates 152, 154 and 156 that extend radiallyfrom a common axis. Plates 154 and 156 are inclined to direct stone toopposite sides of the surge hopper 24. Plate 152 extends upward from andis pivotally secured to plates 154 and 156 at a common axis. Plate 152divides and directs the stone flowing from the horizontal conveyor 80toward plates 154 and 156. Changing the angular position of plate 152alters the proportional flow of stone to plates 154 and 156, andconsequently to opposite sides of the surge hopper 24. A double actingair cylinder 158 driven by the control system in response to datareceived from the stone level sensors 84a-f may be secured to plate 152to provide automated control over its angular position. If the sensors84a-f indicate that one side of the surge hopper 24 is lower than theother, then diverter plate 152 is positioned to increase theproportional flow of stone to the lower side.

II. Stone Metering System

The stone metering system 10 meters and conveys metered quantities ofballast stone to the workheads 22a-d. Referring to FIGS. 1 and 2, thestone metering system 10 is mounted upon the stoneblower 12 and includesa surge hopper 24, a plurality of metering augers 26a-d, and a pluralityof splitters 28a-d.

As discussed above, the surge hopper 24 is fed by the stone replenishingsystem 70 and provides a constant supply of stone to the stone meteringsystem 10. As perhaps best illustrated in FIG. 4, the surge hopper 24has an open top and includes four feed compartments 38a-d. Eachcompartment 38a-d is tapered to feed one of the metering augers 26a-dthrough openings 60a-d in the bottom of each compartment 38a-d.

To provide even distribution of stone throughout compartments 38a-d, arack 170 is mounted for reciprocating motion atop the surge hopper 24(See FIG. 3). The rack 170 is slidably received within a pair ofC-shaped guideways 172a-b. The rack 170 is secured to a reciprocatingrack cylinder 182 and is synchronized to start and stop incorrespondence with the stone replenishing system 70. In a preferredembodiment, the rack 170 includes two longitudinally extending beams174a-b that are received within guideways 172a-b. Two pairs of crosstubes 176a-b extend between opposite longitudinal end portions of beams174a-b. When the stone piled in the surge hopper 24 extends above theplane defined by the rack 170, the reciprocating cross tubes 176a-bengage and distribute the stone throughout the hopper 24.

In addition, opposite longitudinal ends of each beam 174a-b includeconventional wear pads (not shown) and a sweep 178a-d. The wear pads areremovably secured to each beam 174a-b to engage the guideways 172a-b andprevent premature wear of the beams 174a-b and guideways 172a-b. Thewear pads may be replaced as necessary to extend the life of the rackassembly. The sweeps 178a-d are comprised of a plate 180a-d that extendsangularly into the guideways 172a-b from the end of each beam 174a-b.The reciprocating motion of the rack 170 causes the plates 180a-d to"sweep" out any stone that may have accumulated within the guideways172a-b.

One metering auger 26a-d is positioned below each of the surge hoppercompartments 38a-d. As perhaps best illustrated in FIG. 5, each meteringauger 26a-d generally includes a casing 44 and an auger screw 40 withvariable pitch and variable diameter flights 42. The casing of themetering auger 44 includes a "U" shaped trough 50 that cooperates with aplurality of cover sections 52a-c to define a cylindrical chamber withinwhich the auger screw 40 is rotatably supported (See FIG. 2). The coversections 52a-c are removable to allow inspection, servicing, andcleaning of the auger 26a-d. In the preferred embodiment, the internaldiameter of the casing 44 is approximately 9.00 inches (228.6 mm), and,as discussed below in more detail, the external diameter of the augerscrew flights 42 is approximately 6.0 inches (15.24 cm). This provides a1.5 inch (38.1 mm) screw-to-casing clearance which allows significantstone movement with reduced torque requirements and lower potential forjamming.

Inlet and outlet openings 46 and 48 extend through the side walls of thecasing 44 adjacent longitudinally opposite ends of the metering augers26a-d. The inlet opening 46 is located in the upper surface of thecasing 44 where it may be aligned with one of the openings 60a-d in thesurge hopper 24 to allow stone to feed into the casing 44 by gravity.The outlet opening 48 is disposed in the lower surface of casing 44 sothat stone will flow from the metering auger. In a preferred embodiment,the auger screw 40 is supported within the casing 44 at the outlet endby an end plate bearing (not shown) and at the inlet end by a drivemotor bearing (not shown).

The auger screw 40 (see FIG. 5) is constructed of sectional flights 42welded to center shaft 54. In the preferred embodiment, the center shaftis two-inch schedule 80 pipe and the screw flights 42 have a maximumdiameter of 6.0 inches (15.24 cm). In order to reduce wear, the screwflights 42 are preferably constructed of an abrasion resistant steel.The pitch of the auger screw flights 42 is approximately 2/3 at theinlet end 40a of the screw near the inlet end of the casing 44. Thepitch is 1 or full along the remaining portion 40b of the screw 40. Theincrease in pitch expands the stone during the conveying process todecrease the production of fines by reducing cross abrasion between thestones. In the presently preferred embodiment, the pitch of the inletend 40a is 4.0 inches; and the pitch of the remaining portion 40b is 6.0inches.

In addition, the last flight 42a adjacent the outlet end 40c of thescrew tapers from the full diameter to the diameter of the center shaft54. The stone naturally rides in the "bottom" of each flight as ittravels up the screw. Without the described tapering, the stone would bedischarged in these bunches as each screw flight emptied. By reducingthe screw diameter at the discharge end, the stone becomes a morecontinuous or uniform flow. This enables the stone to flow from themetering augers 26a-d in a smooth manner.

An encoder 56 is mounted to the outlet end of the casing 44 to allow thecontrol system to monitor the revolutions or rotational movement of theauger screw 40. The preferred dimensions of the auger screw 40 andcasing 44 described above yield an average stone flow rate of 1.32kilograms per revolution. Based on the average flow rate and rotationalmovement of the auger screw 40, the control system determines the amountof stone supplied to the blow tubes and adjusts the speed of the drivemotor 58 accordingly. A variety of encoders capable of convertingrotational movement into electrical signals are well known to those ofordinary skill in the art.

A drive motor 58 is mounted to the inlet end of the casing 44 forengaging and rotatably driving the auger screw 40. In the preferredembodiment, each blowing tube requires anywhere from 0.25 to 1.0kg/second of stone. Because each metering auger 26 supplies stone to twoblowing tubes, each auger 26 must have a delivery range of 0.5-2.0kg/sec, or twice the single tube stone requirements. Based on theabove-noted average flow rate of 1.32 kg/revolution, the auger screw 40must have a speed range of approximately 23 to 91 rotations per minuteto meet the stone delivery requirements. The hydraulic motor 58 iscontrolled by a standard double-solenoid-operated three-position valveallowing reversal of the screw when required to clean or unjam theauger. As is well known to those skilled in the art,pressure-compensated flow controls may be used to maintain smoothrotation of the auger screw 40 under varied torque requirements.

The profile constraints of the maintenance vehicle require that theopenings 60a-d in the surge hopper 24 lie horizontally below thesplitters 28a-d. Accordingly, the metering augers 26a-d are inclinedupward from the inlet end of the casing to lift the stone to thesplitters 28a-d. In a preferred embodiment, the metering augers 26a-dare inclined upward approximately 20 degrees to accommodate the size ofthe surge hopper 24 and the profile of the maintenance vehicle. Theinclination of the auger can be decreased to reduce the development offines and also to reduce the torque requirements on the drive motor.However, in order to do so, the height of the workheads 22a-d or thedepth of the surge hopper 24 must be sacrificed.

The splitters 28a-d include an open top and two adjacent compartments 66and 68 each separated from the other by a splitter wall 70 generallyaligned with the outlet 48 of the corresponding metering auger 26a-d. Onlevel track, the splitter 28a-d is preferably offset from the center ofthe outlet 48 by 0.19 inches. The offset compensates for the stone beingpropelled slightly off center by the auger screw 40. On railroad trackwith significant cant, the offset of the splitter 28a-d may be adjustedto compensate for the angle of the vehicle and provide for accuratedistribution of the stone between the two blow tubes. For example, thestone is accurately split with an offset of 0.62 inches for track cantof 4 degrees and an offset of 1.06 inches for track cant of 8 degrees.The offset of the common wall 70 is controlled by an automated linearactuator 29 incorporated into the control system (See FIGS. 2-3). In thepreferred embodiment, the automated actuator 29 also includes a positionfeedback mechanism 29b, such as a potentiometer, to measure the offsetof the common wall 70. In operation, the position feedback mechanism 29bmeasures the offset of the common wall 70. Based on this measurement,the actuator 29 is either extended or retracted to obtain the desiredoffset for the existing cant.

III. Operation of Auger Embodiment

In operation, the control system (not shown) continually monitors thestone level sensors 84a-f to determine when the supply of stone in thesurge hopper 24 requires replenishing. When the stone level sensors84a-b indicate that the level of stone on either side of the surgehopper 24 is low, the stone replenishing system 70 is activated. Thecontrol system starts the main auger 74, the cleat conveyor 76, thestone scalper 78 and the horizontal conveyor 80. The main auger 74 movesstone out of the main hopper 72 to the cleat conveyor 76. The cleatconveyor 76 carries stone from the main hopper 72 to the stone scalper78.

The stone scalper 78 is of conventional design and filters the stone bya screen that prevents any stones larger than the openings of the screenfrom passing through to the horizontal conveyor 80.

The horizontal conveyor 80 receives the scalped stone and delivers it tothe surge hopper 24. As the stone is expelled from the horizontalconveyor 80, the diverter assembly 150 directs it in proper proportionto opposite sides of the surge hopper 24 as described above. The stonereplenishing system does not stop delivering stone to the surge hopper24 until both high sensors 84a and 84d are activated. In addition, ifeither empty sensor 84c or 84f is activated then the maintenancefunction is halted while the surge hopper 24 is replenished.

Rack 170, mounted in the opening of the surge hopper 24, reciprocates todistribute the ballast stone delivered by the horizontal conveyor evenly24 throughout compartments 38a-d. The ballast stone flows by gravitythrough openings 60a-d into auger inlets 46a-d to provide a constantsupply of stone to the metering augers 26a-d. The auger screws 40a-d arerotatably driven by drive motors 58a-d to carry the stone upward fromthe inlets 46a-d through the metering augers 44a-d along the flights42a-d of the screws 40a-d. The outlet gates 62a-d are opened as rotationof the auger screws 40a-d begins.

The stone expands along auger screws 40a-d as it is driven upward alongthe variable pitch flights 42a-d. Upon reaching the upward extreme ofthe casing 44a-d, the stone is expelled from the metering augers 26a-dthrough outlets 48a-d. The stone flows by gravity into the splitters28a-d where it is evenly divided and fed to the two blow tubes. Whenstone flow is no longer desired, the drive motors 58a-d are stopped andthe outlet gates 62a-d are closed to prevent stone from spilling intothe splitters. As discussed above, encoder 56 provides the controlsystem (not shown) with an accurate measure of the number of revolutionsof the auger screw 40. The amount of stone delivered by the meteringaugers 26a-d is determined by multiplying the revolutions of the augerscrews 40a-d by the average flow rate (i.e. 1.32 kg/revolution).

In addition, fluid pressure build-up in the feed line causes thehydraulic motor 58 to overshoot or continue to rotate for a short periodafter the motor has been shut off (e.g. the hydraulic valve is shutoff). The amount of overshoot is proportional to the speed of the motorprior to shut off. Overshoot adversely affects the accuracy of thesystem by causing additional stone to fall into the splitter.Accordingly, the control system preferably considers an overshootparameter which dictates how far in advance the motor 58 must be shutoff to compensate for the overshoot.

IV. Alternative Ice-Cube Tray Embodiment

In an alternative embodiment of the present invention, the meteringaugers 26a-d are replaced by unique belt-like conveyors 110. With theexception of the stone conveying/metering units, the stoneblower andstone metering system are identical to those described in conjunctionwith the auger embodiment.

A metering conveyor constructed in accordance with the alternativeembodiment is illustrated in FIGS. 6 and 7. The metering conveyor 110includes a conveyor belt 112, a plurality of support rollers 116, asteel slider bed 118 for supporting the conveyor belt, and aconventional drive system, such as a hydraulic motor (not shown).

The conveyor belt 112 is unique and separated into a number ofcompartments 114 by a plurality of intersecting longitudinally andlaterally extending walls 122 and 124. Each of the compartments 114 areprecisely and uniformly sized to hold a specific quantity of stone.Preferably, the belt 112 is approximately 5 inches wide and theindividual compartments 114 are approximately 2 inches wide by 2 incheslong by 1 inch high. A plurality of cuts 126 are made through thelongitudinally extending walls to allow the belt 112 to move around thesupport rollers 118.

A stone distribution plate 130 is positioned above the conveyor 110immediately upstream from the location where the surge hopper 24 feedsthe conveyor belt 112. The exact longitudinal location of thedistribution plate 130 is not critical, and it may alternatively belocated adjacent the upper support roller 122 to level the stoneimmediately prior to dumping.

V. Operation of Alternative Embodiment

The surge hopper 24 feeds stone directly into the compartments 114 ofthe conveyor belt 112. The conveyor belt 112 in turn conveys the stoneupward and expels it into the splitter 28. As the conveyor belt 112carries stone upward, it passes beneath the distribution plate 130 whichlevels and distributes the stone carried in the compartments 114 (SeeFIG. 7) to improve the uniformity of stone within each compartment. Asthe conveyor belt 112 rounds the upper support roller 122, the stone isdumped from the compartments 114 into the corresponding splitter 28.

As in the preferred embodiment, the amount of stone delivered by theconveyors 110 is determined in part by an encoder 56'. In thisembodiment, the encoder 56' monitors the rotational movement of theupper support roller 122 to determine the number of compartments 114dumped into the splitter 28. The control system (not shown) multipliesthe number of compartments 114 dumped into the splitter by the amount ofstone carried by each compartment to determine the total amount of stonedelivered. Alternatively, a sensor (not shown) may be mounted adjacentthe belt 112 to determine the number of compartments 114 passingthereby. Preferably, the sensor is photoelectric. However, a variety ofconventional sensors will suffice.

The above descriptions are those of preferred embodiments of theinvention. Various alterations and changes can be made without departingfrom the spirit and broader aspects of the invention set forth in theappended claims, which are to be interpreted in accordance with theprinciples of patent law, including the Doctrine of Equivalents.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A railroad trackmaintenance vehicle comprising:a superstructure adapted to travel alonga railroad track; at least one workhead carded on said superstructure; aplurality of blow tubes carded on said workhead; a main hopper carded onsaid superstructure; a supply of ballast stones carded in said mainhopper; and a means for moving the ballast stones from the main hopperto the blow tubes including a stone replenishing system, a stonemetering apparatus, and a splitter means for dividing and distributingstone exiting said stone metering apparatus to said blow tubes; saidstone metering apparatus including:a casing defining an inlet and anoutlet through which said ballast stone is received and discharged,respectively, said casing having a uniform diameter between said inletand said outlet inclusive; and a screw rotatably supported within saidcasing for conveying said ballast stone from said inlet to said outlet,said screw having an inlet end proximate said inlet, said screw having aremainder other than said inlet end, said screw including a plurality offlights each having a pitch, said pitch of said flights at said inletend being less than said pitch of said flights at said remainder of saidscrew, whereby flight volume is greater away from said inlet end toexpand said ballast stone and reduce the production of fines within saidstone metering apparatus.
 2. The vehicle as defined in claim 1 whereinsaid screw includes an outlet end proximate said outlet and having adiameter smaller than the diameter of said remainder of said screw toenable a relatively even flow of the ballast stone through said casingoutlet.
 3. A railroad track maintenance vehicle comprising:asuperstructure adapted to travel along a railroad track; at least oneworkhead carried on said superstructure; a plurality of blow tubescarried on said workhead; a main hopper carried on said superstructure;a supply of ballast stones carried in said main hopper; and a means formoving the ballast stones from the main hopper to the blow tubesincluding a stone replenishing system, a stone metering apparatus, and asplitter means for dividing and distributing stone exiting said stonemetering apparatus to said blow tubes; said stone metering apparatusincluding:a casing defining an inlet and an outlet through which saidballast stone is received and discharged, respectively, said casinghaving a uniform diameter between said inlet and said outlet; and ascrew rotatably supported within said casing for conveying said ballaststone from said inlet to said outlet, said screw having an outlet endproximate said outlet, said screw having a remainder other than saidoutlet end, said screw having a non-uniform diameter along its length,said diameter of said outlet end of said screw being less than saiddiameter of said remainder of said screw, whereby said ballast stonesflow together at said outlet end to reduce bunching and providerelatively even flow from said casing outlet.
 4. The vehicle as definedin claim 3 wherein said splitter means includes variable positioningmeans for offsetting said splitter means in relation to said outlet. 5.An improved track maintenance vehicle having a superstructure adapted totravel along a railroad track, at least one workhead carried on saidsuperstructure, a plurality of blow tubes carried on said workhead, asupply of ballast stones carried on said superstructure, a means formoving the ballast stones from the supply of ballast stones to theworkhead, wherein the improvement comprises:said means for moving saidballast stone from said supply of ballast stone to said workheadsincludes a stone metering apparatus supported upon said trackmaintenance vehicle and a splitter means for dividing and distributingstone exiting said stone metering apparatus to said plurality of blowtubes carried on said workhead, said stone metering apparatus comprisinga stone metering auger including a casing having inlet and outletopenings and an auger screw having longitudinally opposite inlet andoutlet ends rotatably housed within said casing, said casing having auniform diameter, said auger screw including flights that increase inpitch as they extend longitudinally along the screw away from said inletend, said auger screw further including flights that decrease indiameter at said outlet end, whereby said increasing pitch reducesproduction of fines within said stone metering apparatus by expandingsaid stone, and further whereby said decreasing diameter reducesbunching of stone by causing said stone to flow together toward saidoutlet end of said stone metering apparatus.
 6. The improved trackmaintenance vehicle of claim 5, said splitter means for dividing anddistributing the stone delivered by said metering auger simultaneouslyto said plurality of blow tubes, and a splitter mounting means formounting said splitter means in proximity to said casing outlet openingwhereby stone expelled from said metering auger passes into saidsplitter means.
 7. The improved track maintenance vehicle of claim 6,further comprising a surge hopper mounted upon said superstructure andhaving an outlet opening in communication with said casing inlet openingwhereby stone delivered to said surge hopper flows into said meteringauger.
 8. The improved track maintenance vehicle of claim 7, whereinsaid splitter mounting means further includes variable positioning meansfor offsetting said splitter means in relation to said casing outletopening.
 9. The improved track maintenance vehicle of claim 8, furthercomprising an outlet gate mounted over said casing outlet opening and agate control means for actuating said outlet gate between a first openposition in which stone may be expelled from said metering auger throughsaid casing outlet opening and a second closed position in which stoneis prevented from being expelled from said metering auger through saidcasing outlet opening.
 10. The improved track maintenance vehicle ofclaim 9, wherein said maintenance vehicle further includes a main hopperfor storing the supply of ballast stones; andwherein said means formoving the ballast stones from the supply of ballast stones to theworkhead further includes a stone replenishing system mounted on saidsuperstructure for moving stone from said main hopper to said surgehopper, said stone replenishing system including a main auger mountedwithin said main hopper for moving stone out of said main hopper, acleat conveyor in proximity to said main hopper for receiving andconveying stone moved out of said main hopper, a stone scalper inproximity to said cleat conveyor for receiving stone conveyed by saidcleat conveyor and screening out excessively large stones, a horizontalconveyor having a first end in proximity to said stone scalper and asecond end in proximity to said surge hopper for receiving scalped stonefrom said stone scalper and conveying the scalped stone to said surgehopper, a control means for activating and deactivating said stonereplenishing system and a plurality of stone level sensors mountedwithin said surge hopper.
 11. A railroad track maintenance vehicle,comprising:a superstructure adapted to travel along a railroad track; atleast one workhead carded on said superstructure; a plurality of blowtubes carded on said workhead; a main hopper carded on saidsuperstructure; a supply of ballast stones carded in said main hopper;and a means for moving the ballast stones from the main hopper to theblow tubes including a stone replenishing system, a stone meteringapparatus, and a splitter means for dividing and distributing stoneexiting said stone metering apparatus to said blow tubes; said stonemetering apparatus including a stone metering auger supported upon saidsuperstructure, said stone metering auger having a casing with inlet andoutlet openings and an auger screw with longitudinally opposite inletand outlet ends rotatably housed within said casing, said casing havinga uniform diameter, said auger screw including flights that decrease indiameter at said outlet end of said auger screw and increase in pitch asthey extend along the length of said screw away from said inlet endtoward said outlet end, whereby said increasing pitch reduces productionof fines within said stone metering apparatus by expanding said stone,and further whereby said decreasing diameter reduces bunching of stoneexiting said stone metering apparatus by causing said stone to flowtogether toward said outlet end.
 12. The track maintenance vehicle ofclaim 11, said splitter means for dividing and distributing the stonedelivered by said metering auger simultaneously to said plurality ofblow tubes, and a splitter mounting means for mounting said splittermeans in proximity to said casing outlet opening whereby stone expelledfrom said metering auger passes into said splitter means.
 13. The trackmaintenance vehicle of claim 12, further comprising a surge hoppermounted upon said superstructure, said surge hopper being incommunication with said stone replenishing system to receive saidballast stone from said main hopper, said surge hopper having an outletopening in communication with said casing inlet opening whereby stonedelivered to said surge hopper by said stone replenishing system flowsinto said metering auger.
 14. The improved track maintenance vehicle ofclaim 13, wherein said splitter mounting means further includes variablepositioning means for offsetting said splitter means in relation to saidcasing outlet opening.
 15. The improved track maintenance vehicle ofclaim 14, further comprising a rack capable of reciprocating motionmounted within said surge hopper to distribute stone delivered by saidstone replenishing system evenly throughout said surge hopper.
 16. Theimproved track maintenance vehicle of claim 15, further comprising anoutlet gate mounted over said casing outlet opening and a gate controlmeans for actuating said outlet gate between a first open position inwhich stone may be expelled from said metering auger through said casingoutlet opening and a second closed position in which stone is preventedfrom being expelled from said metering auger through said casing outletopening.
 17. The improved track maintenance vehicle of claim 16, whereinsaid stone replenishing system includes a main auger mounted within saidmain hopper for moving stone out of said main hopper, a cleat conveyorin proximity to said main hopper for receiving and conveying stone movedout of said main hopper, a stone scalper in proximity to said cleatconveyor for receiving stone conveyed by said cleat conveyor andscreening out excessively large stones, a horizontal conveyor having afirst end in proximity to said stone scalper and a second end inproximity to said surge hopper for receiving scalped stone from saidstone scalper and conveying the scalped stone to said surge hopper, acontrol means for activating and deactivating said stone replenishingsystem and a plurality of stone level sensors mounted within said surgehopper.